The Free On-line Dictionary of Computing (30 December 2018):

GNU superoptimiser

   (GSO) A function sequence generator that uses an exhaustive
   generate-and-test approach to find the shortest instruction
   sequence for a given function.  Written by Torbjorn Granlund
    and Tom Wood.  You have to tell the
   superoptimiser which function and which CPU you want to get
   code for.  This is useful for compiler writers.

   FTP superopt-2.2.tar.Z from a GNU archive site.

   Generates code for DEC Alpha, SPARC, Intel 80386,
   88000, RS/6000, 68000, 29000 and Pyramid (SP, AP and
   XP).

   (1993-02-16)